Effect of NPK compound fertilizer on cassava (Manihot esculenta crantz) yield in ultisols of Sikasso, Mali

Abstract

Cassava is an important food crop grown across Mali which is cultivated on Ultisols in Sikasso region situated in the southern part of the country. The lack of recommended inorganic fertilizer is among the main constraints in cassava production in the country. The N, P and K inorganic fertilization is not well practiced due to its high cost and no effective fertilizer use packages. This study aimed at determining the effect of four NPK fertilizer (15-15-15) rates (0kg, 100kg, 200kg and 300kg) ha-1 applications on the yield of two cassava genotypes. The two genotypes, Bonima (local) and Sika (introduced from Ghana) were used in a randomized complete block design (RCBD) experiment with three replicates in two sites, Finkolo and Loulouni during one rainy season. The fertilizer rates were applied in splits at equal quantity, two weeks after planting and the rest two months later. Analysis of soil nutrients before planting and plant N, P and K uptake were performed to assess the optimum inorganic fertilization rate for higher yield. Data on plant height, numbers of branches, number of stem, stem diameter, number of tubers by plant, fresh tuber weight, and yield efficiency were collected. Data on cassava production input and output per hectare were also collected. Data collected were subjected to analysis of variance using Statistical Analysis System (SAS version 9.3). The Least Significant Difference (LSD) at p=0.05 was used to separate means. On cassava growth parameters, the higher NPK fertilizer rate which was 300 kg ha-1 increased plant height by 29 and 27% compared to the one from 100 kg ha-1 and the control plot respectively at 8 months after planting (MAP). The 300 kg ha-1 had increased also the cassava stem diameter by 25% compared to the control. On yield parameters, the number of tuber per plant and cassava fresh tuber yield increased by 49% and 133% respectively in plot which received 300 kg ha-1 of NPK. A correlation between NPK inorganic fertilizer rates and fresh tuber yield was determined. The number of branches per plant and number of tuber per plant were found to be strongly correlated. The agronomic Nutrient use efficiency (NUE) was found to increase with additional NPK rates up to 300 kg ha-1. The NPK inorganic fertilizer effect was significant on cassava leave phosphorus content. The leave content in nitrogen and potassium were influenced by site effect making Finkolo more favorable. The simple cost-benefit analysis revealed that cassava production is a beneficial activity in the study sites in Sikasso region. In Loulouni and Finkolo the application of 300 Kg ha-1 of inorganic NPK gave 1300.56 $ and 486.26 respectively which were the highest value of the net benefit from one hectare of cassava. These results will form a basis for NPK inorganic fertilizer recommendations in cassava production in Sikasso and policy brief in cassava production in the country.